======Shrink a Potato with Osmosis======


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**Alternative titles:** Potato Strips in Salt Solutions
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====Summary====                   
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====Procedure====  
  - Prepare three cups with 100 mL distilled water each and label them 0 g, 2 g, and 4 g salt; dissolve the measured salt in the latter two cups.
  - Cut uniform potato strips or cores (about 2 inches long and ≥½ inch thick); remove skin, rinse, and trim all to identical length.
  - Record initial length and width/diameter for each strip in a data table (make triplicates if possible).
  - Gently feel and try to bend the strips to note initial texture.
  - Place one strip (or set of three) into each cup; start a 30-minute timer.
  - After 30 minutes, observe the strips in each cup; remove the 0 g strips, blot briefly, note flexibility, and remeasure length and width; record data.
  - Repeat for the 2 g and 4 g cups, recording measurements and qualitative observations.
  - Compare changes among concentrations; identify which strips swelled or shrank and by how much.



====Links==== 
Shrink a Potato with Osmosis – STEM activity - Science Buddies: 
{{youtube>uOaV81WuHqA?}}\\

the potato experiment - osmosis lab - Scientist Cindy: 
{{youtube>YizdHnzr6Bo?}}\\

📄 Shrink a Potato with Osmosis! - Science Buddies: [[https://www.sciencebuddies.org/stem-activities/potato-osmosis]]\\

====Variations====
  * Weigh strips before and after soaking to track mass change alongside size change.
  * Test additional salt levels (for example, 1 g, 3 g, 5 g per 100 mL) to better locate the isotonic point.
  * Extend soak time to 1 hour or overnight and compare with 30-minute results.
  * Graph final length (or mass) vs. salt concentration and find where the curve crosses the starting value (estimated isotonic concentration).
  * Try other produce (carrot, apple) and compare responses.



====Safety Precautions====
  * Use care with sharp tools (apple corer/knife); cut on a stable cutting board under adult supervision.
  * Keep the workspace dry to prevent slipping; clean up spills promptly.
  * Do not eat experimental materials; compost potatoes after use and wash hands.




====Questions to Consider====
  * Why did strips in pure water get longer or firmer? (Pure water is hypotonic to potato cells, so water enters cells by osmosis, increasing turgor.)
  * Why did strips in higher salt shrink or feel floppier? (Those solutions are hypertonic; water leaves cells by osmosis, reducing turgor.)
  * What does it mean if a strip’s size does not change? (The solution is isotonic with the cells—no net water movement.)
  * How would using tap water instead of distilled water affect results? (Dissolved salts in tap water could shift the effective concentration, slightly reducing swelling.)
  * Which measurement—length, width, or mass—is most sensitive to osmosis here? (Mass usually shows the largest percent change because it directly tracks water gain/loss.)